Catheters have been in use for medical procedures for many years. Catheters can be used for medical procedures to examine, diagnose and treat while positioned at a specific location within the body which is otherwise inaccessible without more invasive procedures. During these procedures a catheter is inserted into a vessel near the surface of the body and is guided to a specific location within the body for examination, diagnosis and treatment. For example, one procedure utilizes a catheter to convey an electrical stimulus to a selected location within the human body. Another procedure utilizes a catheter with sensing electrodes to monitor various forms of electrical activity in the human body.
Catheters are also used increasingly for medical procedures involving the human heart. Typically, the catheter is inserted in an artery or vein in the leg, neck or arm of the patient and threaded, sometimes with the aid of a guidewire or introducer, through the vessels until a distal tip of the catheter reaches the desired location for the medical procedure in the heart.
A typical human heart includes a right ventricle, a right atrium, a left ventricle and a left atrium. The right atrium is in fluid communication with the superior vena cava and the inferior vena cava. The atrioventricular septum separates the right atrium from the right ventricle. The tricuspid valve contained within the atrioventricular septum provides communication between the right atrium and the right ventricle.
In the normal heart, contraction and relaxation of the heart muscle (myocardium) takes place in an organized fashion as electro-chemical signals pass sequentially through the myocardium from the sinoatrial (SA) node to the atrioventricular (AV) node and then along a well defined route which includes the His-Purkinje system into the left and right ventricles. The AV node lies near the ostium of the coronary sinus in the interatrial septum in the right atrium. The His-Purkinje system begins at the AV node and follows along the membranous interatrial septum toward the tricuspid valve through the atrioventricular septum and into the membranous interventricular septum. At about the middle of the interventricular septum, the His-Purkinje system splits into right and left branches which straddle the summit of the muscular part of the interventricular septum.
Sometimes abnormal rhythms occur in the heart which are referred to generally as arrhythmia. For example, a common arrhythmia is Wolff-Parkinson-White syndrome (W-P-W). The cause of W-P-W is generally believed to be the existence of an anomalous conduction pathway or pathways that connect the atrial muscle tissue directly to the ventricular muscle tissue, thus bypassing the normal His-Purkinje system. These pathways are usually located in the fibrous tissue that connects the atrium and the ventricle.
Other abnormal arrhythmias sometimes occur in the atria, which are referred to as atrial arrhythmia. Three of the most common atrial arrhythmia are ectopic atrial tachycardia, atrial fibrillation and atrial flutter. Atrial fibrillation can result in significant patient discomfort and even death because of a number of associated problems, including: an irregular heart rate which causes patient discomfort and anxiety, loss of synchronous atrioventricular contractions which compromises cardiac hemodynamics resulting in varying levels of congestive heart failure, and stasis of blood flow, which increases the likelihood of thromboembolism.
Efforts to alleviate these problems in the past have included significant usage of pharmacological treatments. While pharmacological treatments are sometimes effective, in some circumstances drug therapy has had only limited effectiveness and is frequently plagued with side effects, such as dizziness, nausea, vision problems and other difficulties.
An increasingly common medical procedure for the treatment of certain types of cardiac arrhythmia is catheter ablation. During conventional catheter ablation procedures an energy source is placed in contact with cardiac tissue to heat the tissue and create a permanent scar or lesion. During one procedure the lesions are designed to interrupt existing conduction pathways commonly associated with arrhythmias within the heart. The particular area for ablation depends on the type of underlying arrhythmia. One common ablation procedure treats atrioventricular nodal reentrant tachycardia (AVNRT). Ablation of fast or slow AV nodal pathways is disclosed in Singer, I., et al., "Catheter Ablation for Arrhythmias" Clinical Manual of Electrophysiology, pgs. 421-431 (1993). The use of electrode catheters for ablating specific locations within the heart has also been disclosed, for example in U.S. Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 5,281,217.
Another medical procedure using ablation catheters with sheaths to ablate accessory pathways associated with W-P-W utilizing both a transseptal and retrograde approach is discussed in Saul, J. P., et al. "Catheter Ablation of Accessory Atrioventricular Pathways in Young Patients: Use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach" Journal of the American College of Cardiology, Vol. 21, no. 3, pgs. 571-583 (Mar. 1, 1993). Other catheter ablation procedures are disclosed in Swartz, J. F. "Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites" Circulation, Vol. 87, no. 2, pgs. 487-499 (February, 1993).
Ablation of a specific location within the heart requires the precise placement of the ablation catheter within the heart. Precise positioning of the ablation catheter is especially difficult because of the physiology of the heart, particularly because the heart continues to beat throughout the ablation procedures. Commonly, the choice of placement of the catheter is determined by a combination of electrophysiological guidance and fluoroscopy (placement of the catheter in relation to known features of the heart which are marked by radiopaque diagnostic catheters which are placed in or at known anatomical structures, such as the coronary sinus, high right atrium and the right ventricle).
Ablation procedures using guiding introducers to guide an ablation catheter to a particular location in the heart for treatment of atrial arrhythmia have been disclosed in U.S. Pat. Nos. 5,497,774, 5,427,119, 5,575,166, 5,640,955, 5,564,440 and 5,628,316. During these procedures, ablation lesions are produced in the heart as an element of the medical procedure.
The energy necessary to ablate cardiac tissue and create a permanent lesion can be provided from a number of different sources. Originally direct current was utilized although laser, microwave, ultrasound and forms of direct current (high energy, low energy and fulgutronization procedures) have also been utilized to perform ablation procedures. However, because of problems associated with the use of DC current, radiofrequency (RF) has become the preferred source of energy for ablation procedures. The use of RF energy for ablation has been disclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229, 5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. The use of RF energy with an ablation catheter contained within a transseptal sheath for the treatment of W-P-W in the left atrium is disclosed in Swartz, J. F. et al. "Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites" Circulation Vol. 87, pgs. 487-499 (1993). See also Tracey, C. N. "Radio Frequency Catheter Ablation of Ectopic Atrial Tachycardia Using Paced Activation Sequence Mapping" J. Am. Coll. Cardiol. Vol. 21, pgs. 910-917 (1993).
In addition to radiofrequency ablation catheters, thermal ablation catheters have been disclosed. During thermal ablation procedures a heating element, secured to the distal end of a catheter, heats thermally conductive fluid, which fluid then contacts the human tissue to raise its temperature for a sufficient period of time to ablate the tissue. A method and device for thermal ablation using heat transfer is disclosed in U.S. Pat. No. 5,433,708. Another thermal ablation procedure utilizing a thermal electrode secured to a catheter and located within a balloon with openings in that balloon to permit heated conductive fluid introduced into the balloon from the catheter to escape from the balloon for contact with the tissue to be ablated is disclosed in U.S. Pat. No. 5,505,730.
Conventional ablation procedures utilize a single distal electrode secured to the tip of an ablation catheter. Increasingly, however, cardiac ablation procedures utilize multiple electrodes affixed to the catheter body. These ablation catheters often contain a distal tip electrode and a plurality of ring electrodes as disclosed in U.S. Pat. Nos. 5,582,609, 5,487,385, 5,228,442, 4,892,102, 5,025,786, 5,327,905, and 5,354,297.
To form linear lesions within the heart using a conventional ablation tip electrode requires the utilization of procedures such as a "drag burn". During this procedure, while ablating energy is supplied to the tip electrode, the tip electrode is drawn across the tissue to be ablated, producing a line of ablation. Alternatively, a series of points of ablation are formed in a line created by moving the tip electrode incremental distances across the cardiac tissue. The effectiveness of these procedures depends on a number of variables including the position and contact pressure of the tip electrode of the ablation catheter against the cardiac tissue, the time that the tip electrode of the ablation catheter is placed against the tissue, the amount of coagulum that is generated as a result of heat generated during the ablation procedure and other variables associated with a beating heart, especially an erratically beating heart. Unless an uninterrupted track of cardiac tissue is ablated, unablated tissue or incompletely ablated tissue may remain electrically active, permitting the continuation of the reentry circuit which causes the arrhythmia.
It has been discovered that more efficient ablation may be achieved if a linear lesion of cardiac tissue is formed during a single ablation procedure. The production of linear lesions in the heart by use of an ablation catheter is disclosed in U.S. Patent Nos. 5,487,385, 5,582,609 and Ser. No. 08/407,448. A specific series of linear lesions formed in the atria for the treatment of atrial arrhythmia are disclosed in U.S. Pat. No. 5,575,766.
The ablation catheters commonly used to perform these ablation procedures produce scar tissue at a selected location by physical contact of the cardiac tissue with an electrode of the ablation catheter. Conventional tip electrodes with adjacent ring electrodes cannot perform this type of procedure, however, because of the high amount of energy that is necessary to ablate sufficient tissue to produce a complete linear lesion. Also, conventional ring electrodes may leave holes or gaps in the linear ablation lesion when used to ablate cardiac tissue, which can provide a doorway through the lesion for the creation of a new reentry circuit.
An ablation catheter for use in the heart which contains a pair of intertwined helical electrodes is disclosed in U.S. Pat. No. 5,334,193. The helically wound electrode is affixed to the surface of the catheter body over a distance of about 8 cm. from the distal tip of the catheter body. Other helical electrodes are disclosed in U.S. Pat. Nos. 5,542,928, 4,776,334, 5,047,026, 4,934,049, 4,860,769, and 4,161,952 and WO 95/10319.
During conventional ablation procedures, the ablating energy is delivered directly to the cardiac tissue by an electrode on the catheter placed against the surface of the tissue to raise the temperature of the tissue to be ablated. This rise in tissue temperature also causes a rise in the temperature of blood surrounding the electrode, which often results in the formation of coagulum on the electrode, which reduces the efficiency of the ablation electrode.
To achieve efficient and effective ablation, coagulation of blood that is common with conventional ablation catheters should be avoided. This coagulation problem can be especially significant when linear ablation lesions or tracks are produced because such linear ablation procedures conventionally take more time than ablation procedures ablating only a single location.
It is accordingly an aspect of the invention to disclose a catheter for ablating tissue within the human heart.
It is a still further aspect of the invention to disclose a catheter containing one or more electrodes located within a lumen in the catheter body useful for creating linear ablation lesions.
It is a still further aspect of the invention to disclose an ablation catheter containing one or more electrodes located within a lumen in the catheter and a plurality of openings in the surface of the catheter body in communication with the electrode.
It is a still further aspect of the invention to disclose an ablation catheter containing one or more electrodes located within a lumen in the catheter, a plurality of openings in the surface of the catheter in communication with the electrodes and a structure for the introduction of a conductive media through the lumen to contact the electrodes and then be expelled from openings in the catheter body.
It is a still further aspect of the invention to disclose an ablation catheter useful for formation of a linear ablation lesion within the heart utilizing a catheter body containing one or more electrodes located within a lumen in the catheter body, conductive media passing through the lumen conductively in contact with the electrodes, and openings in the catheter body through which the conductive media passes to contact cardiac tissue for ablation.
It is a still further aspect of the invention to disclose an ablation catheter containing a catheter body with one or more coiled electrodes located within a lumen, a plurality of openings in the surface of the catheter body in communication with the coiled electrodes and the lumen, a conductive media passing through the lumen substantially in contact with the coiled electrodes and a structure in the catheter body which controls the flow of the conductive media through the openings in the surface of the catheter body.
It is a still further aspect of the invention to disclose an ablation catheter for use in the formation of a linear ablation lesion within the heart utilizing a catheter body containing one or more electrodes located within a lumen in the catheter body, conductive media passing through the lumen substantially in contact with the electrodes, openings in the catheter body through which the conductive media passes to contact cardiac tissue for ablation and a structure for guiding the catheter to the location to be ablated.
It is a still further aspect of the invention to disclose an ablation catheter for use in the formation of a linear ablation lesion within the heart utilizing a catheter body containing one or more electrodes located within a lumen in the catheter body, conductive media passing through the lumen, wherein the conductive media is substantially in contact with the electrodes, openings in the catheter body through which the conductive media passes to contact the cardiac tissue to be ablated and a rail for guiding the ablation catheter to the location to be ablated.
It is a still further aspect of the invention to disclose an ablation catheter for use in the formation of a linear ablation lesion within the heart utilizing a catheter body containing one or more electrodes located within a lumen in the catheter body, conductive media passing through the lumen wherein the conductive media is substantially in contact with the electrodes, openings in the catheter body through which the conductive media passes to ablate the cardiac tissue and a guidewire for guiding the ablation catheter to the location to be ablated.
It is a still further aspect of the invention to disclose a method for ablation of cardiac tissue by use of an ablation catheter containing one or more electrodes within a lumen in a catheter body by passing conductive media through the lumen where the conductive media is substantially in contact with the electrode and expelling the conductive media through the openings in the catheter body to contact the cardiac tissue for ablation.
These and other aspects of the invention can be provided by the catheter for the mapping and ablation of cardiac tissue which is disclosed by the present invention.